The present invention relates to dental endosteal implants.
Dental, endosteal implants have been used in recent years which have been rigidly affixed by bone ingrowth with the aid of serrated or porous portions in the body of the implant. Such implants are described in several publications including Hassler et al, "Surgical Tooth Implants, Combat and Field", Reports No. 7 and 8, Contract No. DADA17-69-C-9181 (November, 1976 and December 1977), Hassler et al, "Ceramic Tooth Implants in Baboons", Journal Dent. Res., 56A, A117 (1977), and Hassler et al, "Ceramic Tooth Implants in Baboons", Trans. Soc. of Biomaterials, 2, 114 (1978). In addition, U.S. Pat. No. 3,950,850 (issued to Driskell et al on Apr. 20, 1976) discloses dental implants which are suitable for surgical implantation and which include serrated portions in the body thereof.
While the implants described in the Driskell et al patent and the Hassler et al publications (all of which are specifically incorporated herein by reference) have been successfully used in a clinical environment, the use of implants has presented certain problems which prevent conventional dental implants from achieving universal acceptance. For example, failures of the implants have sometimes occurred during the period after implantation when the surrounding bone has grown sufficiently to provide proper support for the implant. Specifically, in those implants which employ a serrated portion to provide support as a result of bone ingrowth, the cross-sectional dimension of certain portions of the implant body is lessened due to the serrations, thus correspondingly reducing the ability of the implant body to withstand transverse loads of large magnitude which are placed upon it. Thus, the implanted bodies are susceptible to fracturing in the area of the bone line along those portions of the implant having the least cross-sectional dimension.
The lessened cross-sectional dimension of certain portions of the implant due to the presence of the serrations can also present other problems. It is difficult to provide serrated dental implant bodies which do not exhibit a certain minimum cross-sectional dimension since the strength of the implant body and its resistance to fracturing would be decreased. Accordingly, it has not been feasible to provide serrated dental implant bodies which are small enough to be implanted into a bone structure which would not normally accommodate an implant of conventional dimension.
In addition, the bone surrounding the implant body frequently atrophies near the upper portion of the implant body (i.e., near the aveolar crest), thus causing a "cratering" effect. The upper portion of the implant body is thus not sufficiently supported by the bone subsequent to implantation and any movement of the upper portion due to a transverse load placed thereon may cause the lower implanted portion to fracture as a result of a "levering" effect.